1. Technical Field
The present invention relates to a method of separating a GaN substrate by wet etching. Particularly, the present invention relates to a method of separating a GaN substrate, in which n-GaN columns are formed to provide a light emitting diode (LED) structure and are subjected to wet etching using a KOH solution to separate the substrate.
2. Description of the Related Art
Light emitting diodes (LEDs) are semiconductor devices that emit light. With various characteristics such as low power consumption and long lifespan, horizontal type LEDs are used in large color display boards or display screens of mobile phones. However, since the horizontal type LED has an n-type electrode and a p-type electrode formed on the same plane, it is necessary to have a predetermined chip area or higher. Moreover, as the horizontal type LED is fabricated on a sapphire substrate that is an insulator, the horizontal type LED exhibits low brightness in high output operation and is vulnerable to electrostatic shock, thereby providing difficulty in application to general lighting fixtures or vehicle lamps. In recent years, vertical type LEDs overcoming such problems of the horizontal type LEDs are fabricated and used in the art. Vertical type LEDs enable high light output based on good efficiency in heat dissipation and current spreading, and are widely used for high output LEDs.
However, such a typical type LED is fabricated through a laser lift-off process, which requires expensive equipment, thereby causing increase in fabrication costs and a complicated fabrication process. Moreover, in the laser lift-off process, semiconductor layers can be bent due to difference in coefficient of thermal expansion. Therefore, there is a need for novel technology capable of securing productivity.
Korean Patent Publication No. 2012-0099544 A discloses a method of fabricating a vertical type light emitting diode using a wet-etching type buffer layer. In this method, a buffer layer permitting wet etching is interposed between a sapphire substrate and a gallium nitride layer, thereby allowing the sapphire substrate to be removed without laser irradiation. However, in fabrication of a vertical type gallium nitride (GaN)-based LED, there is difficulty in epitaxial growth of GaN due to a large difference between a material for the buffer layer and an n-type semiconductor layer formed on the buffer layer.